Anodic Copper Dissolution

Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over two years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 µg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 µg/L As removed per kWh) compared to before cleaning (72.9 µg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales.

Anodic dissolution of synthetic chalcocite (previously obtained by copper precipitation with S and SO 2 in ammonia media) in two different electrolytic cells is described. One cell has a circular graphite anode placed horizontally, surrounded by a stainless steel cylinder as cathode, and the other has a rectangular basketshaped graphite anode, with a rectangular stainless steel cathode placed in front of it. The electrolysis was performed at 0.2 A and 50 °C, the electrolyte contained 20 to 40 g L-1 of Cu and 100 to 160 g L-1 of H 2 SO 4 , and the initial reactions took place at low potential (0.4-0.6 V) until the transformation of Cu 2 S into CuS, detected by the considerable increase in cell potential. Anodic and cathodic efficiencies greater than 100% and 95%, respectively, were obtained. The hight anodic efficiencie is due to faradic and chemical dissolution too. It is also shown that the (CuS) produced as waste material can replace elemental sulphur as copper precipitating agent in ammoniacal media.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Impurities and additives play a key role in copper electrodeposition, in particular in upstream processes such as electrowinning or electrorefining. One common impurity is iron, mostly present as iron species Fe(II) in highly concentrated sulfuric acid solutions and in a cathodic environment. Herein, the kinetics of copper electrodeposition from such solutions have been investigated using a copper rotating disk electrode and alternating current voltammetry (ACV). For a concentration of proton of 1.84 M and a concentration of Fe(II) ions of 0.054 M, the deposition kinetics are slow enough to separately observe the two electron transfer steps involved in copper reduction: an observation unique to ACV. The results suggest that Fe(II) ions affect the electrodeposition kinetic by slowing down reaction kinetics, in particular slowing the second electron transfer reaction.

Anodic dissolution of synthetic chalcocite (previously obtained by copper precipitation with S and SO 2 in ammonia media) in two different electrolytic cells is described. One cell has a circular graphite anode placed horizontally, surrounded by a stainless steel cylinder as cathode, and the other has a rectangular basketshaped graphite anode, with a rectangular stainless steel cathode placed in front of it. The electrolysis was performed at 0.2 A and 50 °C, the electrolyte contained 20 to 40 g L-1 of Cu and 100 to 160 g L-1 of H 2 SO 4 , and the initial reactions took place at low potential (0.4-0.6 V) until the transformation of Cu 2 S into CuS, detected by the considerable increase in cell potential. Anodic and cathodic efficiencies greater than 100% and 95%, respectively, were obtained. The hight anodic efficiencie is due to faradic and chemical dissolution too. It is also shown that the (CuS) produced as waste material can replace elemental sulphur as copper precipitating agent in ammoniacal media.

Complex oscillatory behavior of electric current and electrode potential were observed during potentiodynamic anodic polarization of Cu in 1 M TFA, applying the current interrupt method for IR drop compensation. This oscillatory behavior was found to give an electrochemical response in the form of a polarization curve with continuous loop. The results presented show that the current interrupt method is capable of eliminating the entire IR drop. Under such conditions, oscillations of the applied potential are in fact those of the double-layer potential. Theoretically predicted interplay between oscillatory behavior of the double-layer potential and the electric current is experimentally demonstrated.

Cu-Pb, Cu-Cd, and Cu-Zn thin films were electrodeposited from a simulated chloride wastewater solution using stainless steel rotating disc electrode. The linear sweep voltammograms of the single metallic ions show that electrodeposition of these ions was under mass transfer control due to the welldefined plateau observed under different rotations. The voltammograms of binary systems elucidate the possibility of selective separation of copper from these binary systems. Currents transients measurements, anodic linear sweep voltammetry (ALSV) and atomic force microscopy (AFM) were used to characterize the electrocryatalization process and morphology of these thin films. ALSV profiles show a differentiation for the dissolution process of individual metals and binary systems. Two peaks of dissolution Cu-Pb film was observed while three and four peaks observed for Cu-Cd and Cu-Zn films respectively indicating different phases have been existed. The model of Scharifker and Hills was used to analyze the current transients and it revealed that Cu-Pb and Cu-Cd electrocrystalization processes are governed by three-dimensional progressive nucleation controlled by diffusion, while Cu-Zn electrocrystallization process starts as a progressive nucleation then switch to instantaneous nucleation process for t/t m >3.AFM images reveal that Cu-Pb film is more roughness than Cu-Cd and Cu-Zn films.

The anodic behaviour of copper in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea or formamidine disulphide was investigated at 298 K, combining data from electrochemical polarisation, chemical analysis, UV-vis spectroscopy, XPS and EDAX analysis, and structural information on copper-thiourea complexes. The main reactions depend on the applied potential and initial thiourea concentration. In the potential range − 0.305 E5 0.075 V (versus SCE), the electro-oxidation of thiourea to formamidine disulphide, the formation of Cu(I)-thiourea soluble complexes, and Cu(I)-thiourea complex polymer-like films, are the most relevant processes. The formation of this film depends on certain critical thiourea/copper ion molar concentration ratios at the reaction interface. At low positive potentials, the former reaction is under intermediate kinetic control, with the diffusion of thiourea from the solution playing a key role. For E] 0.075 V, soluble Cu(II) ions in the solution are formed and the anodic film is gradually changed to another one consisting of copper sulphide and residual copper. The new film assists the localised electrodissolution of copper. A complex reaction pathway for copper anodisation in these media for the low and high potential range is advanced.

Anodic dissolution of synthetic chalcocite (previously obtained by copper precipitation with S and SO 2 in ammonia media) in two different electrolytic cells is described. One cell has a circular graphite anode placed horizontally, surrounded by a stainless steel cylinder as cathode, and the other has a rectangular basketshaped graphite anode, with a rectangular stainless steel cathode placed in front of it. The electrolysis was performed at 0.2 A and 50 °C, the electrolyte contained 20 to 40 g L-1 of Cu and 100 to 160 g L-1 of H 2 SO 4 , and the initial reactions took place at low potential (0.4-0.6 V) until the transformation of Cu 2 S into CuS, detected by the considerable increase in cell potential. Anodic and cathodic efficiencies greater than 100% and 95%, respectively, were obtained. The hight anodic efficiencie is due to faradic and chemical dissolution too. It is also shown that the (CuS) produced as waste material can replace elemental sulphur as copper precipitating agent in ammoniacal media.

Impurities and additives play a key role in copper electrodeposition, in particular in upstream processes such as electrowinning or electrorefining. One common impurity is iron, mostly present as iron species Fe(II) in highly concentrated sulfuric acid solutions and in a cathodic environment. Herein, the kinetics of copper electrodeposition from such solutions have been investigated using a copper rotating disk electrode and alternating current voltammetry (ACV). For a concentration of proton of 1.84 M and a concentration of Fe(II) ions of 0.054 M, the deposition kinetics are slow enough to separately observe the two electron transfer steps involved in copper reduction: an observation unique to ACV. The results suggest that Fe(II) ions affect the electrodeposition kinetic by slowing down reaction kinetics, in particular slowing the second electron transfer reaction.

A coupled multiphysics phase field framework is proposed to model anodic dissolution induced by stress corrosion fracture growth at microstructual level. The effects of electrochemical-mechanical processes (including crystal anisotropy) are all taken into account. This new model is based upon: (i) an anisotropic phase transformation model based on a variational formulation to describe material dissolution along preferential directions; (ii) an efficient description of grain boundaries as a smeared cohesive zone; (iii) an explicit approximation to model the different electrochemical behaviors between grain boundary and grain interior. Both intergranular and transgranular stress corrosion cracking is simulated in an efficient manner. The abilities of the proposed model are illustrated through several numerical examples involving a full prediction of complex crack network growth induced by stress corrosion cracking within 2D polycrystaline models.

A coupled multiphysics phase field framework is proposed to model anodic dissolution induced by stress corrosion fracture growth at microstructual level. The effects of electrochemical-mechanical processes (including crystal anisotropy) are all taken into account. This new model is based upon: (i) an anisotropic phase transformation model based on a variational formulation to describe material dissolution along preferential directions; (ii) an efficient description of grain boundaries as a smeared cohesive zone; (iii) an explicit approximation to model the different electrochemical behaviors between grain boundary and grain interior. Both intergranular and transgranular stress corrosion cracking is simulated in an efficient manner. The abilities of the proposed model are illustrated through several numerical examples involving a full prediction of complex crack network growth induced by stress corrosion cracking within 2D polycrystaline models.

Finally, emerging applications in microelectronics, e.g., through silicon vias for 3D chip stacking and 3D capacitors with dramatically enhanced value for unit area, are among the new critical challenges that silicon microstructuring technologies are facing today. [8,9] Both these applications require the development of novel high-aspect-ratio structures that are well beyond values attainable by commercial technologies (aspect ratio AR < 40). On the other hand, state-of-theart technologies able to control microfabrication at higher aspect-ratios (AR > 100) are limited in terms of etching rate, which is usually restricted to below 2 µm min −1 when the aspect-ratio increases over 20. Figure 1 groups experimental data on etching rate versus aspect-ratio value typical of the principal commercial and research microfabrication technologies, according to authors' best knowledge. Prior results define an unattainable region that is inaccessible for silicon microfabrication technologies, either at commercial or research level (gray area in Figure 1). Its boundary is quite reasonably well described by a power law ER = a AR b , as estimated from experimental data available on the different microfabrication technologies, where ER is the growth rate in µm min −1 , AR is the aspect ratio, and a and b are fitting parameters (a = 23.9 µm min −1 and b = −0.55 on the basis of data available on Figure 1). Time-multiplexed etching (TMEP) process, also known as Bosch process, is the leading microfabrication technology at industrial level. [10] It relies on alternating etching and passivation (polymerization) steps, e.g., using SF 6 as etch gas and C 4 F 8 and Ar as polymerization gases. In spite of TMEP being highly reliable and greatly flexible, TMEP features an aspect-ratio dependent etching rate (ARDE). [11] ARDE usually limits AR of microfabricated pores in the range from 1 to 16 at etching rates from 6 to 3 µm min −1 , respectively (black stars in Figure 1). Although ARDE is less restrictive for trenches, their aspect ratio is also limited to a maximum value of 21 at etching rate of about 4 µm min −1 (green squares in Figure 1). Metal-assisted chemical etching (MaCE) is a novel microfabrication technology that allows targeting AR of 30 though at etching rate <1 µm min −1 (red upside-down triangles in Figure 1). [12-14] MaCE makes use of HF-H 2 O 2 solutions to catalyze chemical silicon dissolution in correspondence with noble metal (e.g., Pt, Au) sites patterned on the silicon

In the present work, we studied the effect of critical electrogalvanizing parameters on the quality of electrodeposited Zn films. The current density, electrodeposition time, and ZnCl2 concentration of electrolyte were optimized to maximize current efficiency and brightness, and also, to minimize the surface roughness. Importantly, regression models of the response variables were developed. These models could help industrial applications by providing definitive process conditions to obtain Zn coatings at a desired thickness, roughness and brightness with a high current efficiency. First, preliminary studies were conducted to determine the initial levels of the designated factors. Then, the optimization was conducted through the Central Composite Design by Design-Expert (trial version). Upon completion of the optimization, analysis of variance was also performed. The optimum values of current density, coating duration and ZnCl2 concentration were determined as 3.7 A/dm 2 , 4.4 minutes, and 50 g/L, respectively, at a thickness of 6 m. Finally, a set of Zn films were deposited at this optimum conditions. The characterization of these films showed that the experimental results were in good accordance with model predictions, providing a bright (L*=83.69) and smooth (Ra=0.75 µm) coating with excellent adhesion to steel substrate (pull-off strength > 29.4 MPa) at a current efficiency of 98.7%.

Combining concepts of semiconductor physics and corrosion science, we develop a novel approach that allows us to perform ab initio calculations under controlled potentiostat conditions for electrochemical systems. The proposed approach can be straightforwardly applied in standard density functional theory codes. To demonstrate the performance and the opportunities opened by this approach, we study the chemical reactions that take place during initial corrosion at the water-Mg interface under anodic polarization. Based on this insight, we derive an atomistic model that explains the origin of the anodic hydrogen evolution.

The electrolytic extraction of liquid copper at 1105 • C from a molten sulfide electrolyte composed of 57 wt% BaS and 43 wt% Cu 2 S was investigated. DC cyclic voltammetry, Fourier transformed AC voltammetry, and galvanostatic electrolysis revealed that the electrodeposition of copper is possible in the selected molten sulfide electrolyte. The half wave potential for the reaction on graphite was determined, and liquid copper of high purity was obtained by galvanostatic electrolysis. These preliminary results confirm that molten sulfides free of alkaline elements could be used as an electrolyte for faradaic applications, despite the semi-conducting nature of the melt. In addition to demonstrating the need for enhanced understanding of the transport properties of such electrolyte, the results show the critical impact of the cell design to improve the process faradaic efficiency.

Impurities and additives play a key role in copper electrodeposition, in particular in upstream processes such as electrowinning or electrorefining. One common impurity is iron, mostly present as iron species Fe(II) in highly concentrated sulfuric acid solutions and in a cathodic environment. Herein, the kinetics of copper electrodeposition from such solutions have been investigated using a copper rotating disk electrode and alternating current voltammetry (ACV). For a concentration of proton of 1.84 M and a concentration of Fe(II) ions of 0.054 M, the deposition kinetics are slow enough to separately observe the two electron transfer steps involved in copper reduction: an observation unique to ACV. The results suggest that Fe(II) ions affect the electrodeposition kinetic by slowing down reaction kinetics, in particular slowing the second electron transfer reaction.

Anodic dissolution of synthetic chalcocite (previously obtained by copper precipitation with S and SO 2 in ammonia media) in two different electrolytic cells is described. One cell has a circular graphite anode placed horizontally, surrounded by a stainless steel cylinder as cathode, and the other has a rectangular basketshaped graphite anode, with a rectangular stainless steel cathode placed in front of it. The electrolysis was performed at 0.2 A and 50 °C, the electrolyte contained 20 to 40 g L -1 of Cu and 100 to 160 g L -1 of H 2 SO 4 , and the initial reactions took place at low potential (0.4-0.6 V) until the transformation of Cu 2 S into CuS, detected by the considerable increase in cell potential. Anodic and cathodic efficiencies greater than 100% and 95%, respectively, were obtained. The hight anodic efficiencie is due to faradic and chemical dissolution too. It is also shown that the (CuS) produced as waste material can replace elemental sulphur as copper precipitating agent in ammoniacal media.

The formation of anodic films during the anodisation of copper, at different applied potentials E, in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea was investigated following the corroding electrode profile by on line in situ imaging. For E B0.07 V (vs. SCE) the electro-oxidation of thiourea to formamidine disulphide and the electrodissolution of copper to Cu(I)-thiourea complexes, including the formation of a polymer-like Cu(I)-thiourea complex (film I), take place. For E\0.07 V, the main reactions are the electro-decomposition of formamidine disulphide and Cu(I)-thiourea complexes yielding a copper sulphide-containing film (film II) and the electrodissolution of copper as aqueous Cu(II) ions through film II. The relative contribution of these processes depends on thiourea concentration in the solution, the applied electric potential and anodisation time. The growth kinetics of films I and II were determined from the evolution of the average film height h obtained from in situ imaging. The kinetics of film I fit a parabolic rate law, whereas those of film II approach a linear h versus anodisation time relationship. The rupture of film II assists the localised corrosion of copper. Likely physical mechanisms for the formation of these anodic films are discussed.

The formation of anodic films during the anodisation of copper, at different applied potentials E, in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea was investigated following the corroding electrode profile by on line in situ imaging. For E &lt; 0.07 V (vs. SCE) the electro-oxidation of thiourea to formamidine disulphide and the electrodissolution of copper to Cu(I)-thiourea complexes, including the formation of a polymer-like Cu(I)-thiourea complex (film I), take place. For E &gt; 0.07 V, the main reactions are the electro-decomposition of formamidine disulphide and Cu(I)-thiourea complexes yielding a copper sulphide-containing film (film II) and the electrodissolution of copper as aqueous Cu(II) ions through film II. The relative contribution of these processes depends on thiourea concentration in the solution, the applied electric potential and anodisation time. The growth kinetics of films I and II were determined from the evolution of the avera...

The anodic behaviour of copper in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea or formamidine disulphide was investigated at 298 K, combining data from electrochemical polarisation, chemical analysis, UV-vis spectroscopy, XPS and EDAX analysis, and structural information on copper-thiourea complexes. The main reactions depend on the applied potential and initial thiourea concentration. In the potential range − 0.305 E5 0.075 V (versus SCE), the electro-oxidation of thiourea to formamidine disulphide, the formation of Cu(I)-thiourea soluble complexes, and Cu(I)-thiourea complex polymer-like films, are the most relevant processes. The formation of this film depends on certain critical thiourea/copper ion molar concentration ratios at the reaction interface. At low positive potentials, the former reaction is under intermediate kinetic control, with the diffusion of thiourea from the solution playing a key role. For E] 0.075 V, soluble Cu(II) ions in the solution are formed and the anodic film is gradually changed to another one consisting of copper sulphide and residual copper. The new film assists the localised electrodissolution of copper. A complex reaction pathway for copper anodisation in these media for the low and high potential range is advanced.